However, these settings are not permanent. If you reboot the system or if you just need to upgrade/downgrade your port speed, run the ehtool command once your port change by network administrator. (If you want to read about how to make Windows 2000/2003 server port speed change, read my previous article.)

Save and close the system. It will set the eth0 device to 100Mbs, full duplex, with the auto negotiation off at boot time. You can simply restart the networking (it will disconnect all ssh or ftp session) or restart the server. Depend upon traffic and load it may take upto 1 minute to setup a new port speed:# /etc/init.d/network restart

If you want 1000Mbs set line as follows:ETHTOOL_OPTS="speed 1000 duplex full autoneg off"Update: if above command failed to work for 1000Mbps use following command (see below in comment sections for discussion) :ETHTOOL_OPTS="speed 1000 duplex full autoneg on"